1. Field of the Invention
The present invention relates to surgical instruments.
2. Description of the Background of the Invention
Trajectory guidance systems are used in surgical procedures to create a stable guide for an operator, such as a surgeon, to increase precision of movement of a work instrument within confines of a highly sensitive region, such as a brain. The system includes a trajectory guide, which defines a stabilized trajectory to precisely guide a work instrument, such as a probe or other surgical instrument, toward a selected position in the body beyond the trajectory guide.
Many trajectory guidance systems are framed guidance systems, which include a large mounting frame that is fixedly mounted to an exterior side of a patient's skull with screws and pins surrounding an entry aperture, or “burr hole,” through the skull. An adjustable guide member, such as a ball and socket with a guide bore, is carried by the frame adjacent or above the burr hole. The surgeon adjusts the guide member within the fixed frame so that the guide bore is axially aligned along a trajectory selected to precisely guide a surgical tool through the entry aperture toward a selected point on an interior side of the skull.
Other known trajectory guidance systems include frameless guidance systems, which dispense with the mounting frame described above, and rather use a small base portion with a guide member having a central bore therethrough. The base portion is secured with screws or bolts to the patient's skull over an entry aperture therethrough. A guide/holding tool is rotatably mounted to the base and includes an arcuate guide rail spaced above the base. A guide holder defining a guide bore is slidably carried by the arcuate guide rail whereby the guide bore circumscribes a range of trajectories that extend through the central bore and the entry aperture.
In another frameless guidance system, the base portion has an externally threaded stud and a central bore therethrough, wherein the stud screws directly into the entry aperture through the skull. The trajectory defined by the guide is adjusted by means of a removable ball and socket joint above the entry aperture.
Both the framed and frameless guidance systems previously known require at least a first procedure to attach the frame or base to the patient and a second procedure to fix the trajectory guide in a selected orientation with respect to the patient. Further, the angular range of adjustable motion of the trajectory may be limited by the size of the entry aperture because the pivot point of the trajectory is generally outside the entry aperture. Thus, a larger, more invasive entry aperture may be needed if a larger angular range of adjustable motion is desired.